Category Archives: Intel

SYSENTER, Where Are You?

Posted on July 20, 2017 by Michal Necasek

It has only recently been brought to my attention that Intel’s SYSENTER/SYSEXIT instructions have rather unusual past, and their origin is shrouded in mystery and confusion. One facet of the usage of these instructions is also a little unorthodox. Depending … Continue reading →

Posted in Intel, PC history, Undocumented | 26 Comments

SGDT/SIDT Fiction and Reality

Posted on May 4, 2017 by Michal Necasek

PSA: Actual hardware behavior takes precedence over vendor documentation. Or, as they say… trust but verify. A reader recently complained how Intel and AMD do not implement the SGDT and SIDT instructions the same way. AMD documentation states that these … Continue reading →

Posted in 286, 386, AMD, Documentation, Intel | 39 Comments

How the PC Industry Screws Things Up

Posted on April 7, 2017 by Michal Necasek

I was recently involved in investigating a problem that turns out to be a complete SNAFU which nicely illustrates the chaos that is the PC platform. It’s about the NX/XD bit. Let’s start with a bit of history. It turns … Continue reading →

Posted in AMD, Intel, Microsoft | 37 Comments

Something New Every Day…

Posted on March 26, 2017 by Michal Necasek

Apparently in 1990, Intel still sold complete systems, and they were PC compatible at that point. And perhaps not surprisingly, Intel also OEMed MS OS/2 1.21: And there was this cute ASCII-art logo: There very little customization that Intel did, … Continue reading →

Posted in Intel, OS/2 | 14 Comments

There’s More to the 286 XENIX Story

Posted on March 22, 2017 by Michal Necasek

It turns out that there is a rather interesting story behind the 286 XENIX incompatibility with 386 and later processors. Here’s roughly what happened in chronological order. In 1982, Intel released the iAPX 286 processor, later known as the 80286 or simply 286. This … Continue reading →

Posted in 286, 386, Intel, Microsoft | 42 Comments

PCI Corner Case

Posted on March 20, 2017 by Michal Necasek

Last weekend I had the pleasure of debugging a curious case of older PCI configuration code (circa 2005) failing on newer (post-2010) hardware. The code was well tested on many 1990s and 2000s PCs (and some non-PCs) with PCI/AGP/PCIe and never … Continue reading →

Posted in Bugs, Intel, PCI | 11 Comments

Top of the Class 478

Posted on January 26, 2017 by Michal Necasek

So I have that old Intel D865PERL board, which is a Socket 478/AGP board. There’s a 3.2 GHz Northwood in it but of course I was wondering, what’s the fastest CPU this board supports? And it turns out to be a … Continue reading →

Posted in Intel, PC hardware, PC history, Pentium 4 | 5 Comments

Mystery NetBurst

Posted on November 28, 2016 by Michal Necasek

Some time ago, a mysterious CPU showed up at the OS/2 Museum: It is a Socket 775 CPU with a Pentium 4 label and the following markings: 3.73 GHZ/1M/1066/A4. In other words, 3.73 GHz clock speed, 1 MB L2 cache, … Continue reading →

Posted in Intel, Pentium 4 | 34 Comments

Intel OverDrive Part III: Pentium II OverDrive

Posted on October 16, 2016 by Michal Necasek

Pentium II OverDrive The Pentium II OverDrive, released in August 1998, was the swan song of the OverDrive product line. It is suitable for Socket 8 systems as an upgrade of 150-200 MHz Pentium Pro processors. Only one model was sold with … Continue reading →

Posted in Intel, Pentium II, Pentium Pro | 19 Comments

Intel OverDrive Part II: Pentium OverDrive

Posted on June 30, 2016 by Michal Necasek

The Pentium OverDrive is notable for supporting three physically different sockets (that’s not counting the Pentium II OverDrive). The Pentium OverDrive product was sold in variants suitable for Socket 2/3 (486 systems), Socket 4 (early Pentium systems), and Socket 5/7 … Continue reading →

Posted in 486, Intel, PC history, Pentium | 21 Comments